The RE200 is usually very easy to set up, but if you are having trouble, the quickest way is to use the WPS button. Plug the extender near your router and press the WPS button on your main router for just a second. Be careful not to hold the button for too long, as on many models it is shared with the Reset function, and you don't want to accidentally wipe your router's settings. After that, immediately press the WPS button on the RE200. If the WPS method fails, I recommend using the TP-Link Tether app. Connect your phone to the extender's default Wi-Fi (usually TP-Link_Extender) and follow the simple steps in the app. Just a tip: always finish the setup in the same room as your router first, and once the connection is successful, you can move the extender to another spot.